pi-gen

Tool used to create the raspberrypi.org Raspbian images

TODO

1. Documentation

Dependencies

On Debian-based systems:

apt-get install quilt parted realpath qemu-user-static debootstrap zerofree pxz zip \
dosfstools bsdtar libcap2-bin grep rsync

The file depends contains a list of tools needed. The format of this package is <tool>[:<debian-package>].

Config

Upon execution, build.sh will source the file config in the current working directory. This bash shell fragment is intended to set needed environment variables.

The following environment variables are supported:

• IMG_NAME required (Default: unset)

  The name of the image to build with the current stage directories. Setting IMG_NAME=Raspbian is logical for an unmodified RPi-Distro/pi-gen build, but you should use something else for a customized version. Export files in stages may add suffixes to IMG_NAME.

• APT_PROXY (Default: unset)

  If you require the use of an apt proxy, set it here. This proxy setting will not be included in the image, making it safe to use an apt-cacher or similar package for development.

  If you have Docker installed, you can set up a local apt caching proxy to like speed up subsequent builds like this:

  docker-compose up -d
  echo 'APT_PROXY=http://172.17.0.1:3142' >> config
  

• BASE_DIR (Default: location of build.sh)

  CAUTION: Currently, changing this value will probably break build.sh

  Top-level directory for pi-gen. Contains stage directories, build scripts, and by default both work and deployment directories.

• WORK_DIR (Default: "$BASE_DIR/work")

  Directory in which pi-gen builds the target system. This value can be changed if you have a suitably large, fast storage location for stages to be built and cached. Note, WORK_DIR stores a complete copy of the target system for each build stage, amounting to tens of gigabytes in the case of Raspbian.

• DEPLOY_DIR (Default: "$BASE_DIR/deploy")

  Output directory for target system images and NOOBS bundles.

A simple example for building Raspbian:

IMG_NAME='Raspbian'

Docker Build

vi config         # Edit your config file. See above.
./build-docker.sh

If everything goes well, your finished image will be in the deploy/ folder. You can then remove the build container with docker rm -v pigen_work

If something breaks along the line, you can edit the corresponding scripts, and continue:

CONTINUE=1 ./build-docker.sh

There is a possibility that even when running from a docker container, the installation of qemu-user-static will silently fail when building the image because binfmt-support must be enabled on the underlying kernel. An easy fix is to ensure binfmt-support is installed on the host machine before starting the ./build-docker.sh script (or using your own docker build solution).

Stage Anatomy

Raspbian Stage Overview

The build of Raspbian is divided up into several stages for logical clarity and modularity. This causes some initial complexity, but it simplifies maintenance and allows for more easy customization.

• Stage 0 - bootstrap. The primary purpose of this stage is to create a usable filesystem. This is accomplished largely through the use of debootstrap, which creates a minimal filesystem suitable for use as a base.tgz on Debian systems. This stage also configures apt settings and installs raspberrypi-bootloader which is missed by debootstrap. The minimal core is installed but not configured, and the system will not quite boot yet.

• Stage 1 - truly minimal system. This stage makes the system bootable by installing system files like /etc/fstab, configures the bootloader, makes the network operable, and installs packages like raspi-config. At this stage the system should boot to a local console from which you have the means to perform basic tasks needed to configure and install the system. This is as minimal as a system can possibly get, and its arguably not really usable yet in a traditional sense yet. Still, if you want minimal, this is minimal and the rest you could reasonably do yourself as sysadmin.

• Stage 2 - lite system. This stage produces the Raspbian-Lite image. It installs some optimized memory functions, sets timezone and charmap defaults, installs fake-hwclock and ntp, wifi and bluetooth support, dphys-swapfile, and other basics for managing the hardware. It also creates necessary groups and gives the pi user access to sudo and the standard console hardware permission groups.

  There are a few tools that may not make a whole lot of sense here for development purposes on a minimal system such as basic Python and Lua packages as well as the build-essential package. They are lumped right in with more essential packages presently, though they need not be with pi-gen. These are understandable for Raspbian's target audience, but if you were looking for something between truly minimal and Raspbian-Lite, here's where you start trimming.

• Stage 3 - desktop system. Here's where you get the full desktop system with X11 and LXDE, web browsers, git for development, Raspbian custom UI enhancements, etc. This is a base desktop system, with some development tools installed.

• Stage 4 - Raspbian system meant to fit on a 4GB card. More development tools, an email client, learning tools like Scratch, specialized packages like sonic-pi, system documentation, office productivity, etc. This is the stage that installs all of the things that make Raspbian friendly to new users.

• Stage 5 - The official Raspbian Desktop image. Right now only adds Mathematica.

Stage specification

If you wish to build up to a specified stage (such as building up to stage 2 for a lite system), place an empty file named SKIP in each of the ./stage directories you wish not to include.

Then remove the EXPORT* files from ./stage4 (if building up to stage 2) or from ./stage2 (if building a minimal system).

# Example for building a lite system
echo "IMG_NAME='Raspbian'" > config
touch ./stage3/SKIP ./stage4/SKIP ./stage5/SKIP
rm stage4/EXPORT*
sudo ./build.sh  # or ./build-docker.sh

If you wish to build further configurations upon (for example) the lite system, you can also delete the contents of ./stage3 and ./stage4 and replace with your own contents in the same format.